This project is an historical cohort study whose primary aim is to quantify the risks of breast and gynecologic cancers among a group of women exposed to DES and/or other non-steroidal estrogens during pregnancy compared with a group that was not exposed. Its specific aims are: 1. To quantify relative and attributable incidence rates of breast and gynecolgic cancers, benign breast disease, and total mortality for women exposed to DES during pregnancy. 2. To identify and adjust for relevant confounding variables to be explored including family history of breast cancer, menstrual history, parity, age at termination of first pregnancy, and other exogenous estrogen use. 3. To describe the pathologic features of any tumors associated with DES use. 4. To describe the occurrence of cancers other than breast or gynecologic in the exposed and unexposed groups. This project is a collaborative study among four institutions (Baylor College of Medicine, the Mayo Foundation, Massachusetts General Hospital, and Dartmouth-Hithcock Medical Center). It dovetails with the DESAD Project, which is a collaborative observational study of the health effects of DES on women exposed in utero. We anticipate following a cohort comprised of 3000 women exposed to DES during pregnancy and 3000 unexposed women. They will be contacted to ascertain diagnosed cancers and obtain information on known risk factors.